You currently have 50,000 customers and over the years the level of variability in what a customer has spent each year has consistently had a standard deviation of $6,000. You only have time to talk to 9 customers and ask each what they plan to spend next year. Their responses were (in $1,000): 44, 78, 58, 94, 81, 63, 40, 100, 72. Hint: Remember the discussion on the Central Limit Theorem. Page 199 of class notes.

a. What is the point estimate of total sales?

b. Determine a 95% confidence interval for total sales?